A G4S employee who sent an anonymous letter to his boss threatening to blow up vans and demanding £1m has been warned he faces a "significant sentence" after being convicted of blackmail at Teesside Crown Court.
Daniel Garland, 19, caused work to halt at the cash-handling depot in Thornaby, Teesside, when he posted the menacing note in January saying he had planted remotely-controlled "mini-bombs" on vehicles.<
More than 100 police officers joined a major inquiry across four force areas, cash-in-transit vans were recalled to the depot to be searched and the security giant's losses were put at £15,000, the court heard.
Garland, from Durham Place, Chester-le-Street, County Durham, had admitted a bomb hoax charge and was convicted after a trial of a blackmail offence.
The jury heard how branch manager Dean Jeffels was terrified when he read the letter which threatened to detonate bombs placed on employees' cars and on work vehicles.
The letter told the manager robbers would storm the depot with weapons if £1m was not loaded onto a truck outside the depot the next day.
It also warned of visiting a mother and her new-born baby while her partner - a G4S employee - was at work.
Garland said in his defence that he had been bullied at work and the motivation for writing the letter was merely to get the two named colleagues into trouble, and perhaps a move away from his section.
A jury deliberated for more than five hours and convicted him by a majority of 10 to two of blackmail.
Recorder Euan Duff remanded him in custody to be sentenced at Durham Crown Court on September 29.
He said: "A significant sentence is inevitable."
Outside court Chief Superintendent Alistair Simpson said a major operation to reassure the public, check the safety of the depot and vehicles and to protect named employees had to be put in place.